1. Field of the Invention
The present invention relates to a microfluidic device which electrochemically regulates a pH of a fluid therein and a method of regulating the pH of the fluid in a microfluidic device.
2. Description of the Related Art
A microfluidic device includes an inlet, an outlet, a reaction chamber, and a microchannel connecting the inlet, the outlet, and the reaction chamber. The microfluidic device also includes a micropump for transferring fluids, a micromixer for mixing the fluids, a microfilter for filtering the fluids, and other additional components, in addition to the microchannel.
Microfluidic devices are well known to those of ordinary skill in the art and are used in microanalysis devices such as lab-on-a-chips (“LOCs”), which perform a series of biological analysis processes including cell enrichment, cell lysis, biomolecule refinement, nucleic acid amplification and separation, protein separation, hybridization reaction, and detection.
Each step needs a different pH in order to perform the various biological analysis processes as described above. A conventional method of regulating pH in a biological analysis process is performed by adding or removing an acid solution, a basic solution, a neutral solution or a buffer solution. However, when regulating pH, the addition or removal of such a pH-regulating solution in a microfluidic device requires a separate device and process. Also, a sample solution in the microfluidic device is undesirably diluted.
Such problems regarding the addition of a pH-regulating solution or the need for a separate device may be serious in a microfluidic device using microvolumes. In addition, the dilution can also be a problem when taking or amplifying a target sample. Moreover, when the added pH-regulating material may act as an inhibitor in a later performed biological analysis process, the added pH-regulating material should be removed to prevent unreliable results.
Electrolysis may be used as a method for solving the problems arising with the conventional method of externally injecting a pH-regulating reagent. For example, a pH can be regulated using an electrolytic device including an anode chamber, a cathode chamber, and a separation membrane between the anode and cathode chambers.
However, in the conventional method, when a solution flowing into the chambers contacts the separation membrane, the separation membrane swells, and thus changes in shape and size, thereby leading to a change in volume of the chambers. In addition, due to the small size of the electrodes, there is a large difference in resistance between the electrodes. Furthermore, an electric current flows locally through the chamber, and thus leads to a higher pH near the anode. Thus, pH cannot be uniformly regulated. In addition, pH in each of the chambers changes too slowly to enable efficient biological assays such as a cell lysis process.